In general, a wind turbine or a wind turbine park is operated with the aim to obtain maximum yield of the capital invested in it, and consequently the wind turbine control systems are configured to maximize the output power, i.e. to operate the wind turbine to capture the maximal power that is available in the wind, with due regard to keeping the wind turbine within operational limits.
While the control system of the wind turbine is designed to take into account the various and varying conditions that a wind turbine operates under, a wind turbine normally further includes a safety system. The safety system aims to preserve the structural integrity in case of unforeseen events, component failures, or other problems that may require that the turbine is operated in a controlled safe-mode, be that a reduced production mode or a shutdown of the turbine.
Existing wind turbine safety systems are based on measurements of a small subset of the turbine states, such as rotor speed, tower-top acceleration and load measurement. The safety system normally compares the measured values with predefined limits which are considered to be safe. If outside the predefined limits, the wind turbine is shut down or operated in a reduced power production mode. This entails that existing safety systems react only when faults or extreme events have evolved to a level where predefined physical or mechanical limits are exceeded. This creates an inherent need for increased structural strength to accommodate the loads following such late detection of fault conditions.
In a different approach, the wind turbine may obtain data from a plurality of sensors and use these data to predict whether or not the turbine is about to exceed the predefined structural limits. However, since safety related electronic equipment needs to be certified for safety use, such equipment is expensive. Moreover, predictive algorithms are complicated and require high performing computing equipment. As a consequence, the computing tasks of the safety system are limited in complexity.
The inventors of the present invention have realized that there is a need for further ways of operating a wind turbine in a safe way.